I have just re-read the explanation on ‘conjunct vs conjunction’ you gave me last academic year, and things are becoming clearer to me.
Two more questions though, you said that ‘adverbial conjuncts’ such as ‘yet’, ‘so’ and ‘therefore’ are called so because they link SENTENCES whether ‘coordinating conjunctions’ are used to link CLAUSES. But ‘yet’ and ‘so’ ARE coordination conjunctions, aren’t they - c.f. ‘FAN BOYS’;
On the other hand, in a book -“Academic Writing” by Hogue and Oshima - they call ‘therefore’, ‘however’, nevertheless, etc, ‘conjunctive adverbs’, is that wrong ?
You seem to call ‘”when, where, how and why” ‘conjunctive adverbs’ are they the same as ‘relative adverbs’ ?

I have created my own grammar lessons thanks to the clarifications and examples you all gave me and I’d like to thank you again for that.
Here I am again this year, and I hope our collaboration will be as fruitful.

Hela - a tricky area, this, since even among grammarians there is some terminological discrepancy.

1. Re. yet & so: strictly speaking, these are not (or, at least, should not be classified as) coordinating conjunctions, for the simple reason that they can be prefixed by 'and' (a coordinating conjunction), while no true coordinating conjunction can ever be directly preceded by another.

Thus we may have

[1] It was raining BUT they went out.

[1a] It was raining; YET they went out.

[1b] It was raining and YET they went out.

but not

[1c] *It was raining and BUT they went out.

demonstrating that 'but' is a true conjunction, while 'yet' is not.

The same applies to 'so'.

2. Re. 'therefore' etc.: while most grammarians recognize essentially the same categories of words, the labels that they give them may vary, and, especially when a term already in use by some to designate one set of forms (conjunctive adverbs) is utilized by others to refer to another group (adverbial conjuncts), some confusion is sadly inevitable. Based on my own experience as a teacher and student of languages, the following represents what I would consider to be a generally acceptable overview of English connectives:

represents 'at the time at which', and contrasts clearly with the same word used as a relative or conjunctive (see below).

(2) Since a conjunction can never serve a nominal role (as subject , object, etc.) ,
connectives consisting of or containing 'what, who, which' are never classified as conjunctions.

(3) re. 'how' as a conjunction: although informal usage tolerates such sentences as

Play the piece HOW you played it before.

formal/careful usage would require the full form

....in the (same) way that/in which...

(4) re. the exclusion of 'why': there is no possibility of forming a sentence such as

*I want you to do it WHY you did it last time.

to mean

...for the (same) reason that/for which...

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CONJUNCTS: a sub-class of adverbials (words or phrases serving an adverbial role) that are not true coordinating conjunctions (see above) but may be used to connect - temporally, causally or otherwise - coordinate clauses in the manner of a coordinating conjunction, or even whole sentences.
Examples: then, therefore, nevertheless, for that reason, despite that.

N.B. Unlike coordinating conjunctions, which only ever occur in between clauses, adverbial conjuncts may typically be placed in various positions. Thus we may equally well have However, it was a mistake. or It was, however, a mistake.

CONJUNCTIVES: the set of canonically*** interrogative, non-concessive*** pronouns, adjectives or adverbs used as subordinating clause-connectors: what, who, where, when, why, how, which.
They can be expanded to the form [(prep.)+which/what+(NP)], and occur in clauses that stand as subjects or verbal objects. Like the interrogatives from which they derive, they contain an implied question although may equally well occur in declarative and imperative as in interrogative sentences.

Examples:
Do you know WHAT he did? (= what thing)
Do you remember WHY we came here? (=for what reason)
Tell me HOW you found it! (=in what way)
I asked him WHEN the train would arrive. (=at what time)

(Compare the last with 'when' as a conjunction above).

I need to know WHICH bag you put it in.

***canonically = 'originally', referring to their simplest and most basic use
***non-concessive= except forms ending in (-so)ever

CONNECTIVE CONCESSIVES: the set of connective pronouns, adjectives and adverbs ending in -(so)ever when used to introduce a concessive nominal or adverbial clause.

Examples:
I'll have WHATEVER you're having.
Give it to WHOEVER deserves to have it.
Take WHICHEVER one you like.
(Nominal concessives).

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N.B.
(1) Nominal concessives are pronouns or adjectives representing [any (NP) that] .
(2) Where an inflected pronoun is used, it takes its form according to its role within the clause - i.e. as subject, object or complement - irrespective of the overall role (subject, object, etc.) of the clause itself. Thus, in the second example above, 'whoever' takes the nominative form since it stands as subject of the verb 'deserves', although the nominal clause itself stands as prepositional object. Compare this with

Give it to WHOMEVER you choose.

where the role of the clause is identical but the pronoun now occupies an object position within the clause.
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WHOEVER it may be, don't open the door.
WHICHEVER one you may choose, the price will be the same.
WHEREVER you go, I'll follow you.

(adverbial concessives)

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N.B. Adverbial concessives (which may be pronouns, adjectives or adverbs) typically stand at the beginning of the sentence, and can be expanded to the form 'no matter...' (in the third example 'No matter where you go, I'll follow you').

Compare the use of 'wherever' here as concessive adverb with the same word used as a subordinating conjunction, occurring without a comma, normally in final position, and meaning [in/to any place in/to which], e.g.

(*** a separate use from its more common function as a subordinating conjunction and which may occur only with a limited set of antecedents.)

Relative adjective: which (archaic/legalistic)

Relative adverbs: where, when, why (but not 'how')

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N.B.
(1) Relative adverbs represent reductions of fuller phrases with relative pronouns, and have meanings such 'in which (place), at which (time), for which (reason)'.
they are naturally limited to cooccurrence with antecedent nouns denoting (respectively) time, place or reason.

Compare 'when' as a conjunction and as a conjunctive adverb (see above) with the same word as a relative adverb in

In the year WHEN (=in which) Beethoven was born, the aristocracy still ruled unchallenged.

(2) Although, as stated, 'why' may be a relative adverb, as in

He refused to explain the reason WHY (=for which) he had committed the crime.

there is no corresponding use of 'how', to say e.g.

*This is the way HOW he did it.

rather than

This is the way that/in which he did it.

(3) A special sub-class of relative pronouns, known as sentential relatives, can also take entire clauses as antecedents. Members of this group are 'as' and 'which'.

Examples: He's a very hard worker, AS you well know.

where 'as' represents 'the fact that he is a very hard worker'.

As a sentential, 'as' (but not 'which') can even precede its referent:

AS you well know, he's a very hard worker.

(4) There is a special type of relative clause known as an APPOSITIVE RELATIVE, such as the boldface that-clause above, adjectivally modifying a noun phrase such as 'the fact', yet having also nominal affinities (hence the possibility of its also being considered as 'appositive' to the noun phrase). Note, however, that this 'that' is a conjunction, and not a relative form of any kind.

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NOMINAL RELATIVES: these are any of the words that can function as conjunctives (except 'which') used to introduce a nominal clause standing as copular complement, and expandable to the form [the NP that], called 'relatives' since they are deemed to function like adnominal relatives but to contain their antecedent 'within themselves', so to speak.

This is WHERE he died. (= the place that/in which)
(Cf. 'where' as conjunctive meaning 'in which place').

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N.B.
(1) Although 'which' can function both as a conjunctive adjective and pronoun and as an adnominal relative adjective and pronoun(see above), it has no corresponding use - either pronominal or adjectival - as a nominal relative, since we may not have e.g.

*This is WHICH bag she chose.

for

This is the bag that she chose.

(2) On occasions - according to sense/context rather than any specifically syntactic factors - we may reckon an ostensibly conjunctive clause even when standing as verbal object to be relative rather than conjunctive when it is not intended as an implicit question.

Compare, for instance, the two quite different interpretations possible with respect to

Do you remember WHEN Uncle Graham came to visit?

If we assume the speaker to have forgotten the date and to be requesting that information from us, we will reckon 'when' a conjunctive adverb (= on which day) and reply something like

It was March 25th.

If, on the other hand, we interpret this sentence simply as a pleasant reminiscence, we will treat 'when' instead as a nominal relative adverb (=the day that/on which), and answer quite differently (e.g. "Yes, I do. Wasn't it fun!").

N.B. Re. archaisms 'whence' and 'whither': both may function as adnominal relative and conjunctive adverbs meaning respectively 'from which (place)' and 'to which (place)', but only rarely as conjunctions or as nominal relatives. 'Whence' may additionally stand as a relative pronoun in pleonastic 'from whence'.